1. Field of the Invention
This invention deals with the art of removing black fumes or carbon particles from exhaust gas from an internal combustion engine.
2. Prior Art
In an internal combustion engine and particularly a diesel engine, there has been a demand for an exhaust gas treating device for removing undesirable particles, including carbon particles constituting black fumes, from the exhaust gas discharged from the engine. As is well known, particles dispersed in gas can be arrested or collected by a cyclone, an electric precipitator or a filter, or by the washing with water. The use of the filter is the most effective in removing the black fumes or carbon particles from the exhaust gas. However, in the case where the filter is used in an internal combustion engine which produces a relatively large amount of black fumes, such as a diesel engine, the filter tends to become clogged in a relatively short period of time, so that the engine fails to operate properly. Therefore, in the exhaust gas treating device using the filter, it is frequently necessary to either change or clean the filter element. This requires time and labor.
And, the engine must be stopped each time the filter element is either changed or cleaned. In addition, the carbon particles collected in the filter must be disposed of. Thus, the exhaust gas treating device of this type has not been fully practical.
To overcome this difficulty, there has been proposed an exhaust gas treating device utilizing a heat-resistant filter in which the carbon particles resulting from the black fumes and collected in the heat-resistant filter is burnt by a burner to regenerate the filter. Thus, this device is advantageous in that the engine can be operated continuously and that the carbon particles collected in the filter does not need to be subjected to after-treatment. However, the amount of dissipation of heat to the atmosphere is relatively large in this exhaust gas treating device, and therefore the engine incorporating this device is not suited for an automobile or a civil engineering equipment for use in a closed space such as a tunnel unless the exhaust gas treating device is provided with means for effecting exhaust heat recovery. In addition, since the heat-resistant filter must be heated at elevated temperatures for regeneration, the filter is subjected to frequent heating and cooling particularly when the load of the black fumes or carbon particles is large. As a result, the service life of the heat-resistant filter tends to be shortened.